Controlled thermal cycling treatments have been applied to various alloy metals for a number of years. The most common metals to receive treatment are steel alloys, which normally include two or more alloying elements such as cobalt, nickel, molybdenum, titanium, aluminum, chromium, manganese, magnesium, tungsten and vanadium. It has been found that thermal cycling treatment of such alloy metals improves their resistance to normal wear and tear, which is especially useful in treatment of tools constructed of such metals.
Thermal cycling treatments have also been used to treat electrical power transmission equipment such as wires, cables, electric motors, etc. Such treatments have also recently been discovered by the inventors to be beneficial in the copper welding electrode field. Welding electrodes so treated have exhibited improved voltage conduction and current.
A typical thermal cycling process involves lowering the temperature of the article to be treated to temperatures exceeding -300.degree. F. (-185.degree. C.). The article is then allowed to recover until its temperature is equivalent to its ambient surroundings, or about 72.degree. F. (22.degree. C.). In some cases, the article is then raised to about +300.degree. F. (149.degree. C.) and then allowed to cool gradually back to ambient temperature.
In treatment of alloyed steel components, such thermal cycling processes affect the wearability of the metal by four known mechanisms: conversion of significant amounts of austenite to martensite; precipitation hardening which increases Rockwell hardness; formation of fine carbide particles; and residual stress relief.